diff --git a/release/powerpc/mkisoimages.sh b/release/powerpc/mkisoimages.sh
--- a/release/powerpc/mkisoimages.sh
+++ b/release/powerpc/mkisoimages.sh
@@ -75,7 +75,7 @@
 	# Apple boot code
 	uudecode -p "`dirname "$0"`/hfs-boot.bz2.uu" | bunzip2 > $BOOTBLOCK
 	OFFSET=$(hd $BOOTBLOCK | grep 'Loader START' | cut -f 1 -d ' ')
-	OFFSET=0x$(echo 0x$OFFSET | awk '{printf("%x\n",$1/512);}')
+	OFFSET=$((0x${OFFSET} / 512))
 	dd if="$BASEBITSDIR/boot/loader" of=$BOOTBLOCK seek=$OFFSET conv=notrunc
 
 	bootable="-o bootimage=macppc;$BOOTBLOCK -o no-emul-boot"